A sound recording rarely, if ever, gives a listener the exact same experience as he or she would have had had the listener been present when the sound recording was made. The reasons may include placement, limitations, and/or characteristics of the equipment used to record the sound as originally generated (e.g., a spoken or musical performance in a sound studio or live performance venue); intended and/or unintended effects of the process by which the final sound recording was produced (e.g., processing either performed or not performed and/or other decisions made in the mixing and mastering process); differences between the space in which the sound recording is rendered and the space in which the sound was originally generated and recorded; and limitations and/or characteristics of the playback equipment used to render the audio data embodied in the sound recording to a listener.
Any one or combination of the above factors or possibly other factors may result in a listening experience that does not satisfy fully the subjective taste of a particular listener in one or more respects. For example, the sound recording as rendered may have a high-order perceptual attribute that is not pleasing to the listener, or may lack a high-order perceptual attribute desired by the listener, or the high-order perceptual attribute may be present to a degree not fully pleasing to the listener. As used herein, a “high-order perceptual attribute” is a characteristic of an audio signal associated with a sound recording as rendered to a listener that depends both on (1) the content of the audio signal, as determined both by the original sound recorded to make the sound recording and any processing performed in producing the final sound recording made available to be rendered to the listener, and (2) the characteristics of the playback equipment used to render the audio signal and the effects of any further processing performed on the audio signal prior to its being rendered to the listener. A high-order perceptual attribute is distinguishable from gross attributes, such as loudness, or the presence of noise and/or other unwanted components or artifacts, in that a high-order perceptual attribute describes fine distinctions in the manner in which the essential components of the audio signal are reproduced and rendered while maintaining the basic integrity of the underlying performance, much like the right combination of herbs and spices can bring out different aspects of the flavor of a food or a carefully selected stain can highlight (or deemphasize or mask) features in the grain of a piece of wood in a particular desired way. A high-order perceptual attribute is “perceptual” in the sense that it is discernable to at least a trained or skilled listener, and such a listener can describe at least in relative terms the extent which it is present or not in an audio signal as rendered using reasonably precise language that by usage or convention conveys to other listeners the extent to which a particular recognizable quality is present. Examples of such high-order perceptual attributes as they have been described in sound recording and audio equipment literature, for example, include “punch” (good reproduction of dynamics and good transient response with strong impact); “presence” or “closeness” (the sense that a particular instrument, e.g., is present in the listening room); “warmth” (easy on the ears, not harsh); “spaciousness” (conveying a sense of space, ambiance, or room around the instruments and/or other sound sources); “fatness” (fullness of sound, increased energy in the upper bass region); and “clarity” or “transparency” (easy to hear into the music; detailed, not distorted). Such attributes are inherently subjective and, as such, the rough definitions provided in parentheses above are provided only by way of example.
Once a sound recording has been set in a tangible medium, such as a compact disc or an MP3 or other digital file, or otherwise made available for distribution to and/or use by one or more end listeners, the high-order perceptual attributes of the sound recording in the past have been considered to be fixed, with each end listener having to accept the attributes of the sound recording as provided. Gross tools have been provided to enable users to affect to some limited degree the manner in which a sound recording is rendered, such as a volume control to adjust the loudness, noise reduction technologies to reduce noise, and tools such as bass and treble controls and equalizers to enhance or attenuate sound in particular frequency bands, but many such tools apply the same modification to an audio signal associated with a sound recording regardless of the audio content or otherwise are capable of making only gross adjustments to an audio signal as rendered, and as such are inadequate to affect or provide high-order perceptual attributes, such as those described above. Therefore, there is a need for a way to allow an end listener to modify an audio signal associated with a sound recording in a way that changes a high-order perceptual attribute of the audio signal as rendered.